Answer
a). (3) $tan^{-1}\frac{w}{d}$
b). $27^{\circ}$
Work Step by Step
a). $tan r= \frac{w}{d}$
or, $r=tan^{-1}(\frac{w}{d})$
As per the law of reflection, i=r,
so, $i=tan^{-1}\frac{w}{d}$, option (3) is the answer.
b). $i=tan^{-1}\frac{25cm}{50cm}=tan^{-1}(\frac{1}{2})$
thus, $i=27^{\circ}$
